LED Heatsink Performance

by / Friday, 16 March 2018 / Published in Company Blog

The performance of LED heatsink can be represented by the cooler thermal resistance Rhs. The formula is as follows:


Tmax: LED heatsink maximum temperature (°C);

TA: Ambient temperature (°C);

P: Heat dissipation of LED heatsink (W)

LED heatsink temperature is defined as shown in the figure below

In forced convection cooling system equipment, when the fluid flows through LED heatsink, it will cause a certain pressure loss before and after LED heatsink, so part of the fluid may pass around LED heatsink. This phenomenon is called a fluid bypass heatsink, as shown in the figure below.

When the geometry of LED heatsink changes, such as increasing the number of fins, the surface area A of the heatsink increases. For a fluid by-pass heatsink, after the fins increase to a certain amount, the amount of fluid between the fins decreases, and the corresponding convective heat transfer coefficient h decreases. According to Newton’s cooling law of convection heat to transfer, the increase in heatsink or surface area A will increase the heat dissipation capacity of the heatsink, but the decrease of convection coefficient h will weaken the heatsink capacity. Therefore, the number of fins in LED heatsink has an optimal value.


If the volume of LED heatsink and the number of fins is not changed, the thickness of the heatsink fins will gradually increase, and the fin efficiency will increase correspondingly, that is, the heat dissipation effect will increase. However, after the number of fins is increased to a certain value, the fin spacing will be reduced accordingly, which will result in a decrease in the flow rate and affect the heat dissipation.


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